改性超高分子量聚乙烯的摩擦磨损性能研究

通过添加聚丙烯(PP)和交联聚丙烯(PP-X)对超高分子量聚乙烯(UHMWPE)进行改性,研究了UHMWPE及其共混物的摩擦磨损性能.结果表明,在200 r/min滑动速度下,当PP或PP-X的质量分数为30%时,UHMWPE/PP的摩擦因数降至0.13,降幅达38.1%,磨痕宽度降至5.05 mm;UHMWPE/PP-X的摩擦因数降到0.12,降幅达42.9%,磨痕宽度则降至4.50 mm,UHMWPE/PP-X具有更优异的摩擦磨损性能.负载增大,UHMWPE及其共混物的摩擦磨损性能降低.磨损时间小于60 min,UHMWPE及其共混物的摩擦因数和磨痕宽度变化不大;超过60 min,摩擦因数和磨痕宽度均增大,UHMWPE/PP-X的增幅最小.高速滑动下UHMWPE/PP-X的摩擦磨损性能最高.     

POM/UHMWPE共混物摩擦磨损性能研究

将3种不同的超高摩尔质量聚乙烯(UHMWPE)和聚甲醛(POM)共混，制成POM自润滑材料，并研究了共混物的摩擦磨损性能。结果表明：采用自制的PP改性UHMWPE(M-UHMWPE)与POM共混，能有效提高POM的摩擦磨损性能；当M．UHMWPE质量分数为5％时，POM／M-UHMWPE共混物的摩擦系数从纯POM的0．32降低到共混物的0．16，磨痕宽度从POM的5．00mm下降为3．56mm；SEM分析表明，在摩擦过程中，M-UHMWPE向磨损界面转移形成磨屑，有效地隔离了两摩擦面的接触，起到了减摩耐磨剂的作用，明显降低了POM树脂的摩擦系数，提高了POM的耐磨损性能。     

聚丙烯/超高摩尔质量聚乙烯共混物的结构与性能研究

研究了不同物料比和加工工艺对聚丙烯（PP）／超高摩尔质量聚乙烯（UHMWPE）共混体系性能的影响。结果表明，PP／UHMWPE共混体系具有比音一组分更高的冲击性能，当体系中UHMWPE的质量分数为60％时，共混物的冲击强度高达101kJ/m^2，分别是PP的1．8倍和UHMWPE的1．3倍，将UHMWPE加入PP中可明显降低PP的摩擦系数，提高其耐磨性，而适量UHMWPE加入PP中，对UHMWPE的耐磨性能无不良影响，对以PP为连续相的共混体系，混炼方式对共混物的性能影响大，偏光显微镜分析表明，当PP／UHMWPE共混体系中UHMWPE的质量分数大于40％时，就很难观察到明显的PP大球晶结构，DSC分析显示，PP／UHMWPE共混物出现了两纯组分熔点的结晶熔融峰，PP／UHMWPE为热力学不相容体系。     

聚乙烯/聚丙烯共混体系力学性能的研究

研究了线型低密度聚乙烯（LLDPE）／聚丙烯（PP）共混体系、高密度聚乙烯（HDPE）／PP共混体系、超高相对分子质量聚乙烯（UHMWPE）／PP共混体系的力学性能和熔体流动速率。结果表明，UHMWPE的增韧效果最好，在UHMWPE的质量分数为15％时体系的综合力学性能优异，当UHMWPE质量分数大于15％时，材料的综合性能开始下降。     

增韧剂/纳米CaCO3并用对聚丙烯共混体系力学性能的影响

研究了不同的增韧剂（EPDM、HDPE、LDPE和SBS）对聚丙烯共混物力学性能的影响,EPDM含量为15％时,共混物的拉伸强度下降较小,冲击强度比纯聚丙烯提高450％。采用正交实验法,研究了纳米CaCO3和EPDM并用对PP共混物力学性能的影响,含量6％的纳米CaCO3具有增强和增韧作用;纳米CaCO3与EPDM并用能协同增强聚丙烯;PP／EPDM／纳米CaCO3的质量比为74／20／6时,聚丙烯共混体系的综合力学性能较好。     

超高分子量聚乙烯的改性研究

通过添加PP和自制交联聚丙烯(PP-X),使用双辊开炼和Haake密炼的方法对超高分子量聚乙烯(UHMWPE)进行改性,并通过万能材料试验机、熔体流动速率仪和摩擦磨损试验机等系统研究了UHMWPE、UHMWPE/PP、UHMWPE/PP-X的力学性能、熔体流变性能及摩擦磨损性能等.结果表明,当PP和PP-X的质量分数小于等于30%时,UHMWPE的力学性能得到了一定程度的改善,熔体流动性能增加,摩擦磨损性能有较大提高.     

PP/UHMWPE共混物力学性能的研究

采用不同结构的聚丙烯(PP)分别与不同流动性能的超高摩尔质量聚乙烯(UHMWPE)进行共混，对共混物的力学性能进行了研究。发现PP和UHMWPE类型的适当匹配对共混物性能的提高非常重要。流动性较好的UHMWPE对熔体质量流动速率较小的嵌段共聚型PP(PPB)增韧增强效果突出，常温缺口冲击强度可达74．2kJ／m^2，断裂伸长率大于700％；同时共混物的强度和刚性也有一定程度的提高。在PPB／UHMWPE二元共混物中加入适当线性低密度聚乙烯(LLDPE)，能够起到“减粘”和“增容”作用，有利于共混物性能，尤其是抗冲性能的进一步提高。     

UHMWPE共混改性HDPE薄膜性能的研究

采用中等摩尔质量聚乙烯（MMWPE）首先对超高摩尔质量聚乙烯（UHMWPE）进行改性，然后通过两步共混法制备了HDPE／UHMWPE共混吹塑薄膜，研究了共混物的力学、流变性能以及MMWPE对UHMWPE力学和流变性能的影响。实验结果表明，当改性UHMWPE中的MMWPE的质量分数为40％时，改性UHMWPE的力学性能下降不大，而流变性能大大改善。两步法制得的HDPE／UHMWPE薄膜表面的晶点明显减少，比一步法得到的薄膜的拉伸强度和撕裂强度分别提高了20％和12％，比纯HDPE的分别提高45％和21％。     

聚丙烯/含氟聚丙烯层状共混物的制备

采用熔融接枝技术制备含氟聚丙烯（FPP），然后将聚丙烯（PP）与FPP共混造粒制备PP／FPP共混物。用锥板流变仪分析PP和FPP的流变行为，探讨PP／FPP共混物层状形态形成的条件；用扫描电子显微镜、紫外光测试仪和万能材料试验机分析PP／FPP共混物层状形态、抗紫外光辐射性能和力学性能。结果表明，在200℃．剪切速率为125s^-1时，PP和FPP的流变曲线相交于一点，此条件有利于PP／FPP共混物形成层状形态。与纯PP相比，PP／FPP共混物的力学性能和抗紫外光透过能力明显提高。     

UHMWPE/PP共混物流动性影响的研究

选用三种不同表观黏度的聚丙烯(PP)采用熔融共混的方法制备得到超高摩尔质量聚乙烯(UHMWPE)/PP复合材料。通过调控PP摩尔质量、共混时间以及共混物组成比,分别研究其对UHMWPE流动性的影响。实验结果表明,PP可以有效改善UHMWPE的流动性。PP摩尔质量的降低、共混时间的增加和PP含量增加,均会降低UHMWPE/PP共混物的表观黏度,提升材料的流动性。     

Preparation and properties of poly(Nε,Nε-dicarboxymethyl-l-lysine)

A new ampholytic homopolypeptide, $\text{poly}\text{(N}{}^{\mathrm{\epsilon }}\text{,N}{}^{\mathrm{\epsilon }}\text{-}\text{dicarboxy-methyl-}\text{l}\text{-lysine}\text{)}$, which has one tertiary amino and two carboxyl groups in the side chain has been derived from a hydrochloride salt of poly(L-lysine). The polymer in aqueous solution seems to be in the coil form with locally extended structure (LES) at neutral pH. In both the acidic and alkaline regions, the molar ellipticity of the polymer changes as a result of change in net charge on the side chain. The conformational changes may be from the coil with LES to other coiled forms. 5–7 M NaClO₄ and 80% aqueous methanol induce the α-helix in the polymer at neutral pH. Divalent cations, Cu²⁺ and Ca²⁺, do not induce any remarkably ordered structures such as α-helix or β-structure in the polymer in aqueous solution at any pH. Ultraviolet absorption studies show an absorption peak of the polymer-Cu²⁺ complex near 240 nm. Dependence of the peak intensity on pH at various q values ($\text{q =}\text{[}\text{Cu}{}^{\mathrm{2+}}\text{]}\text{[}\text{residue}\text{]}$) indicates the two steps of the complex formation. At q less than 0.64, the formation is described only with the first step. An average coordination number for Cu²⁺ at the first step was calculated to be about 2 by the method of Mandel and Leyte. The association constant of Cu²⁺ with the residue at the step was determined from the absorption data to be far smaller than that for the Cu²⁺-EDTA complex. The second step of the formation occurs in the case of large q but the absorption data for the second step cannot be obtained exactly due to precipitation.     

Wet Milling of Fe/Al/Al2O3 and Fe2O3/Al/Al2O3 Powder Mixtures

Wet milling of Al₂O₃-aluminide alloy (3A) precursor powders in acetone has been investigated by milling Fe/Al/Al₂O₃ and Fe₂O₃/Al/Al₂O₃ powder mixtures. The influence of the milling process on the physical and chemical properties of the milled powders has been studied. Particle refinement and homogenization were found not to play a dominant role, whereas plastic deformation of the metal particles leads to the formation of dislocations and a highly disarranged polycrystalline structure. Although no chemical reactions among the powder components in Fe₂O₃/Al/Al₂O₃ powder mixtures were observed, the formation of a nanocrystalline, ordered intermetallic FeAl phase in Fe/Al/Al₂O₃ powder mixtures caused by mechanical alloying was detected. Chemical reactions of Fe and Al particle surfaces with the atmosphere and the milling media lead to the formation of highly porous hydroxides on the particle surfaces. Hence the specific surface area of the powders increases, while the powder density decreases during milling. The fraction of Fe oxidized during milling was determined to be 0.13. The fraction of Al oxidized during milling strongly depends on the metal content of the powder mixture. It ranges between 0.4 and 0.8.     

Participation of lewis base on vinyl chloride polymerization with Al(C2H5)3CCl4 catalyst system

The polymerization of vinyl chloride has been investigated using an $\text{Al}\text{(}\text{C}{}_2\text{H}{}_5\text{)}{}_3\text{CCl}{}_4$ catalyst system in the presence of various Lewis bases. Effective Lewis bases are γ-butyrolactone, diglyme and diethylenetriamine which are multidentate. The rate of polymerization is dependent not only on the basicity of the Lewis base used but also on a coordination number of one. The latter is the predominant factor. For the effect of polymeric amines, a tentative hypothesis is discussed.     

Sintering of Si3N4-Y2O3-Al2O3

Sintering kinetics of the system Si₃N4-Y2O₃-Al₂O3 were determined from measurements of the linear shrinkage of pressed disks sintered isothermally at 1500° to 1700°C. Amorphous and crystalline Si₃N₄ were studied with additions of 4 to 17 wt% Y₂O₃ and 4 wt% A1₂O₃. Sintering occurs by a liquid-phase mechanism in which the kinetics exhibit the three stages predicted by Kingery's model. However, the rates during the second stage of the process are higher for all compositions than predicted by the model. X-ray data show the presence of several transient phases which, with sufficient heating, disappear leaving mixtures of β ' -Si₃N₄ and glass or β '-Si₃N₄, α '-Si₃N₄, and glass. The compositions and amounts of the residual glassy phases are estimated.     

Synthesis and Characterization of Ti0.33Ta0.33Nb0.33C and Ti0.33Ta0.33Nb0.33CxN1-x Whiskers

Ta_0.33Ti_0.33Nb_0.33C and Ta_0.33Ti_0.33Nb_0.33C _x N_{1− x} whiskers were synthesized via a carbothermal vapor-liquid-solid growth mechanism in the temperature range 900°-1450°C in Ar or N₂. The optimum temperature was 1250°C. Whiskers were obtained in a yield of 70-90 vol%. The whiskers were 0.5–1 µm in diameter and 10–30 µm in length. The starting materials that produced the highest whisker yield were: TiO₂, Ta₂O₅, Nb₂O₅, C, Ni, and NaCl. C was added to reduce the oxides, and Ni to catalyze whisker growth. NaCl was used as a source of Cl for vapor-phase transportation of Ta and Nb oxochlorides and Ti chlorides to the catalyst. The catalyst metal was recycled several times during the synthesis and was transported as NiCl₂( g ) according to thermodynamic calculations. The rate of formation and the chemical composition of the whiskers depended on the synthesis temperature, the choice of catalyst, and the atmosphere. At low temperatures, the whiskers were enriched in Nb and Ta, whereas the Ti content increased with increased synthesis temperature.